If I were writing about a different part of the U.S., i.e. east or north of us, there might be a dozen species which I'd want to include in this category. As it is, there are relatively few conifers in our area. We are on the very edge of the range for long-needle pines, which grow just to the east of us. Some people do grow them, but they don't grow large or profusely. There are also a few ornamental conifers that do okay, but are not widely seen.
Three conifers are very well-suited to grow here. One is an import. The Chinese arborvitae (Platycladus orientalis or Thuja orientalis) is probably the most commonly used landscape pine in Austin. There is a native arborvitae, which is the white cedar (Thuja occidentalis) but it is better suited to cooler climates and grows mostly in the eastern part of the U.S. Our arborvitae, which is also called bookleaf pine, is not terribly fast growing, but does quite well under very hot and dry conditions. The common name means something like "tree of life" and refers to several different species. The photo at right shows the immature cones and tiny needles that are characteristic of the plant.
These pines are often sold as very small shrubs, but they grow to over 10 feet, given the room. Because of the size discrepancy, many are used in inappropriate places, like close to the eaves of a house or on either side of a driveway. They look nice for a few years, but then become too big and must be cut down. Although arborvitae do not normally need pruning, they can be cut back to form a hedge.
The trees grow as several separate trunks, dividing very close to the ground. During heavy rains, snow and ice storms, the weight of the water may bend the individual trunks and cause the tree to look like it is melting. While it can often recover from such injury, we had one large tree that was bent so badly by ice that it did not regain its original form and had to be removed.
The needles of the arborvitae are tiny and scale-like. They are often brighter green on the tips and have a lovely pattern of vertical branches, which is where they get the name of bookleaf. This growth pattern only occurs when the tree gets a lot of sun. In shade, the branches tend to grow at all angles, giving a more feathery and open appearance.
Like all conifers, arborvitae produce cones. They are a light gray or bluish color when they are young and are fleshy and compact, not resembling the usual pine cone at all. Small curved prongs project from the tips of each scale before the cones open. The seeds are about the size and shape of apple seeds and have a high germination rate. We had numerous baby trees growing in the yard around one large arborvitae, and they were easy to transplant when small.
One of our native conifers is deciduous. The bald cypress (Taxodium distichum)is found along rivers, lakes and streams, and in sheltered, low-lying moist areas. It does well between buildings in an urban setting and also in man-made water retention ponds. In permanent water, the bald cypress can get to be impressive giants, with huge buttressed trunks. However, their growth rate depends on the amount of water they receive and the quality of the soil. They grow incredibly slowly for us. We have three trees which were planted as 12 inch seedlings and the biggest is now about 14 feet tall after 15 years. The smallest is a spindly 6 feet. The cypress trees are crowded by other trees but do get a bit of extra water. Their leaves are a beautiful soft feathery green all summer and they don't suffer significantly from the heat. The photo at left shows a giant swallowtail on the leaves of one of our bald cypresses. None of the trees in our yard have reached sexual maturity yet and so haven't produced cones. In the fall, the leaves turn a rusty brown, then drop.
Cypress wood is considered to be very durable and resists rotting in water. Another feature of cypress trees is the knees that they produce under some conditions. Although thought to aid in oxygen exchange, the real value of these structures is still not understood.
As the cypress are growing, they tend to put out branches at a very low height, so we have periodically trimmed off the lower ones to encourage upwards growth. The trunks of the very young trees also produce the feathery leaves. Once the leaves fall, they make nice mulch, but, if it is dry and they curl up, they tend to cling to our dog's hair like small combs, becoming a nuisance as she unintentionally collects them and brings them into the house.
The last of our conifers is the most contentious one. Ash juniper (Juniperus ashei) grows profusely throughout the Austin area. It has numerous other names, including mountain cedar, blue-berry juniper, Texas cedar, sabino, enebro, cedro, and rock cedar. Although often called cedar, it is not a true cedar at all, but a juniper. The wood is aromatic and has insect repellent qualities. However, I often find insects and spiders on the branches, such as the crab spider hiding in the foliage pictured at right.
Although juniper is a native tree, it used to be less numerous. The plant has responded well to human alteration of the landscape and is now a dominant feature in many areas. The trees can grow in the poorest of soil, with little water, although they grow very slowly. There is a belief that nothing can grow beneath the junipers, even lending the name of cedar sage to a small wildflower that does grow in its shade. Actually, there are plenty of plants that can grow beneath junipers, but few that can grow in as poor soil. Given better soil, the junipers add fine mulch as they shed some of their tiny needles, and also shelter other plants from the blistering sun.
Junipers are named after the Dutch word for gin, which is made from the berries of a related species, Juniperus communis. Produced by the female trees, ash juniper berries are not used for flavoring gin, but can be used as a spice, especially for meat. The tiny blue berries, which are actually the cones, are eaten by birds, even after they have fermented from age on the ground. The main commercial use for junipers is the oil extracted from them, which is both aromatic and a disinfectant.
The principle reason that people despise junipers is their reproductive habits. The sexes are separate and a tree produces either fruit or pollen. It is the male trees producing pollen that has gained the junipers such notoriety. During the winter months, December into February, the male trees release copious quantities of wind-borne pollen to fertilize the female flowers. The clouds of pollen can be so thick that they look like yellow smoke. We notice that our driveway looks as if it is dusted with yellow chalk during this time. Many people have an allergic reaction to the tiny pollen grains, resulting in what is commonly called "cedar fever" with symptoms resembling a cold.
We have several young juniper trees in our yard. They are very easy to start from tiny seedlings or from bird dropped seed. If growing in full sun, the trees grow extremely slowly and tend to branch near the base, producing more of a shrub. However, in crowded and shady conditions, the trees grow more upright, with a single trunk, especially if they are encouraged with regular pruning of the lower lateral branches. All our junipers are at least 12 years old and the tallest is now about 15 feet. Because of constant pruning, they all have straight trunks and well-defined crowns, although those that have grown in the most ideal locations look the nicest. Even the needles of the junipers vary according to conditions. In dense shade, the needles are very prickly, sticking straight out, but in sun, they are more scale-like and small. A single tree can have both types, depending on which parts of the branches get the most sun. Ash junipers can attain a large size, but it takes many years. Many of the oldest trees are in rather inaccessible places, like the rocky slopes by creeks, and they are often interspersed with other species of trees, like live oaks.
While not a spectacular specimen plant, the junipers lend nice variety to a stand of trees, and the blue berries are an interesting seasonal phenomenon, even if the pollen is a nuisance to some.